1. Field of the Invention
The present invention generally relates to a hydraulic brake pressure control system, and more particularly to a hydraulic brake pressure control system which is appropriate to control brake fluid pressure in a hydraulic circuit of a brake system connected to wheels of an automotive vehicle.
2. Description of the Related Art
As disclosed in Japanese Laid-Open Patent Application No. 4-243658, there is known a hydraulic brake pressure control device in which a determination as to whether the hydraulic brake pressure control device is normally operating is made by comparison of a master cylinder pressure and a wheel cylinder pressure. When the hydraulic brake pressure control device of the above publication is normally operating, the wheel cylinder pressure related to a wheel cylinder of an automotive vehicle is adjusted to be proportional to the master cylinder pressure related to a master cylinder of the hydraulic brake pressure control device.
In the hydraulic brake pressure control device of the above publication, when the master cylinder pressure is detected to be above a given pressure and the wheel cylinder pressure is detected to be proportional to the master cylinder pressure, it is determined that the hydraulic brake pressure control device is normally operating.
On the other hand, when the master cylinder pressure is detected to be above the given pressure but the wheel cylinder pressure is detected to below a proper pressure level (or the wheel cylinder pressure does not properly rise in response to the master cylinder pressure), it is determined that a malfunction has occurred in the hydraulic brake pressure control device. Or when the master cylinder pressure is detected to be below the given pressure and the wheel cylinder pressure is detected to be above the proper pressure level, it is determined that a malfunction has occurred in the hydraulic brake pressure control device. By using the detection method of the hydraulic brake pressure control device of the above publication, it is possible to notify a vehicle operator of the occurrence of a malfunction in the hydraulic brake pressure control device.
Generally, in order to perform an effective countermeasure process in response to the occurrence of individual malfunctions in the hydraulic brake pressure control device, it is necessary to quickly find a position of each individual malfunction and a mode of each individual malfunction in the hydraulic brake pressure control device. Hereinafter, such information of each individual malfunction will be called the malfunction position/mode. However, the hydraulic brake pressure control device of the above publication does not detect the malfunction position/mode in the hydraulic brake pressure control device when the occurrence of the malfunction is detected. Hence, it is difficult for the hydraulic brake pressure control device of the above publication to perform an effective countermeasure process in response to the occurrence of individual malfunctions.
An object of the present invention is to provide an improved hydraulic brake pressure control system in which the above-described problems are eliminated.
Another object of the present invention is to provide a hydraulic brake pressure control system which is capable of detecting the malfunction position/mode of each individual malfunction when the occurrence of the malfunction is detected in the hydraulic brake pressure control system, in order to quickly perform an effective countermeasure process in response to the occurrence of the malfunction.
The above-mentioned object of the present invention is achieved by a hydraulic brake pressure control system in which a master cylinder which generates a brake fluid pressure proportional to a brake pedal pressure, a high-pressure supply device which generates an increased brake fluid pressure, and a hydraulic circuit having a wheel cylinder device are provided, the hydraulic circuit performing a master cylinder control to control a wheel cylinder pressure by using the pressure generated by the master cylinder, and performing a brake-by-wire control to control the wheel cylinder pressure by using the pressure generated by the high-pressure supply device, the hydraulic brake pressure control system comprising: a master cut valve device, provided in the hydraulic circuit, which controls a flow of brake fluid from the master cylinder into the wheel cylinder device; a wheel cylinder sensor device which outputs a signal indicative of the brake fluid pressure in the wheel cylinder device; and a malfunction position/mode detecting unit which detects a malfunction position and a malfunction mode in the hydraulic brake pressure control system based on the signal output by the wheel cylinder sensor device during the master cylinder control and the signal output by the wheel cylinder sensor device during the brake-by-wire control.
In the hydraulic brake pressure control system of the present invention, a malfunction position and a malfunction mode of each individual malfunction which may occur in the system are accurately detected based on the output signal of the wheel cylinder sensor device during the master cylinder control and the output signal of the wheel cylinder sensor device during the brake-by-wire control. It is possible for the hydraulic brake pressure control system of the present invention to quickly perform an effective countermeasure process in response to the occurrence of the malfunction.
In the hydraulic brake pressure control system of the present invention, a plurality of countermeasure processes for individual malfunctions are stored. A specific position and a specific mode of each individual malfunction which may occur in the hydraulic brake pressure control system are detected by the malfunction position/mode detecting unit, and it is possible to easily select the most effective countermeasure process for the malfunction of concern from the stored countermeasure processes. Hence, it is possible for the hydraulic brake pressure control system of the present invention to quickly perform an effective countermeasure process in response to the occurrence of each individual malfunction.